Q is around 0, 28 . Low Q is very tight bass.
Combination with the very tight bass from N Core results in almost no bass .

Then raise your system Q; 0.5 is already maximally damped; 0.7 is flat; lower than 0.5 does not make sense and cuts the bass, the loudspeaker is badly tuned.
You can't blame the amplifier.
Any amplifier with decent damping factor will give you a bass shy sound with a 0.28 Q system.

Then raise your system Q; 0.5 is already maximally damped; 0.7 is flat; lower than 0.5 does not make sense and cuts the bass, the loudspeaker is badly tuned.
You can't blame the amplifier.
Any amplifier with decent damping factor will give you a bass shy sound with a 0.28 Q system.

Q is around 0, 28 . Low Q is very tight bass.
Combination with the very tight bass from N Core results in almost no bass .

is this the total Q of a sealed box ?

If it is then you either need to redesign your speaker or increase the effective output impedance of the amplifier or even use a tube amp !! It certainly is no fault of the ncore or any other amp with low output impedance !!